The five-digit number $246\underline{\hspace{5pt}}8$ is divisible by 9. What is the missing digit?
In order for a number to be divisible by 9, the sum of its digits must be divisible by 9. Since $2+4+6+8=20$, the only value of the missing digit that causes the sum of the digits to equal a multiple of 9 is $\boxed{7}$, as $27=9\cdot 3$.